1. Field of the Invention
The present invention relates to a microbe propagation preventing apparatus and a microbe propagation preventing method which enable prevention of microbe propagation in foods or the like by using ions.
2. Description of the Prior Art
FIG. 29 is a perspective view showing a conventional microbe propagation preventing apparatus disclosed in, for example, Japanese Patent Application Laid-Open No. 3-72289. In FIG. 29, reference numeral 1 means an external gas, 2 is a metallic needle electrode made of metallic material such as tungsten, stainless steel, or nickel, 3 is a metallic grid-like electrode, 4 is a high voltage generator to apply high voltage between the metallic needle electrode 2 and the metallic grid-like electrode 3 so as to generate corona discharge, 5 is an ozone decomposing catalyst to decompose ozone contained in the gas 1, and 6 is an ionized gas containing no ozone.
A description will now be given of the operation.
A distance (a gap length) between the metallic needle electrode 2 and the metallic grid-like electrode 3 is set at several centimeters. When the high voltage generator 4 is used to apply dc high voltage in a range of several to over ten but less than twenty kilovolts between the metallic needle electrode 2 and the metallic grid-like electrode 3, the metallic grid-like electrode 3 is positively charged, and the metallic needle electrode 2 is negatively charged. Thereby, an electric field having high intensity is generated at a distal end of a needle of the metallic needle electrode 2, resulting in glow-like discharge having a light color which is called the corona discharge. Thus, the corona discharge negatively ionizes an oxygen molecule in the air in an ionization space. While the negative ion generated by the corona discharge travels to the metallic grid-like electrode 3, ambient air is also carried because of viscosity of the air. As a result, an ionized air flows from the metallic needle electrode 2 toward the metallic grid-like electrode 3.
However, since the external gas 1 contains the oxygen molecule, the corona discharge generates ozone as well as the negative ion. In this connection, high concentration of ozone is harmful because the ozone exhibits intensive oxidization.
Hence, the ozone decomposing catalyst 5 is disposed on the downstream side in an air duct through which the gas containing the ozone flows. The ozone decomposing catalyst 5 removes the ozone from the ionized gas so that the ionized air 6 containing no ozone is discharged into a space.
Since the inventors found that the gas 6 can reduce the propagation of the microbes adhering objects such as foods in case the gas 6 contains an appropriate concentration of ion, the prior art apparatus has been discussed as a microbe propagation preventing apparatus. However, prior to filing of this application, the prior art apparatus is actually disclosed as simply an apparatus to generate ions rather than the apparatus to prevent the microbe propagation by using the ions. A detailed description thereof will be given later.
Alternatively, there is another embodiment as shown in FIG. 30, in which a gas containing the ozone is provided for foods housed in a refrigerator so as to prevent the propagation of the microbe generated in the foods.
In FIG. 30, reference numeral 7 means the refrigerator, 8 means the foods housed in the refrigerator 7, 9 is a cooler of the refrigerator 7, 10 is a gas in the refrigerator 7, 11 is a fan to draw the gas 10, 12 is an ozonizer to generate the ozone by the discharge, 13 is an ozone sterilizing/deodorizing chamber to sterilize and deodorize the microbes such as bacteria, mold and a malodorous component which are contained in the gas 10, 14 is the ozone decomposing catalyst to decompose excess ozone by using, for example, manganese dioxide, and 15 is a clean gas which is sterilized and deodorized.
A description will now be given of the operation.
The refrigerator 7 includes the cooler 9 to cool the inside of the refrigerator 7 in which the foods 8 are housed. On the other hand, the ozonizer 12 injects the ozone to the gas 10 drawn by the fan 11 including the mold, the bacteria, or the malodorous component such that ozone concentration in the gas 10 is in a range of several to tens ppm. In such a way, the ozone is injected into the gas 10, and the gas 10 is introduced into the ozone sterilizing/deodorizing chamber 13 so as to sterilize or deodorize the mold, the bacteria, or the malodorous component which is contained in the gas 10.
However, the gas 10 in the ozone sterilizing/deodorizing chamber 13 contains the ozone with concentration in a range of several to tens ppm. Consequently, when the gas 10 is discharged as it is, the gas 10 is harmful for a human body. Further, there is a risk in that equipments such a heat exchanger, or the fan 11 may corrode due to the ozone (specifically, if the ozone concentration in the refrigerator 7 is increased to a range no less than 0.1 ppm, some kinds of foods may discolor or deteriorate, and the equipments such as the heat exchanger, the fan 11 in the refrigerator 9 corrode). Hence, the gas 10 including relatively high concentration of ozone is introduced into the ozone decomposing catalyst 14 to decompose and remove the ozone so as to reduce the ozone concentration to a range no more than an operation reference value (of 0.1 ppm). Thereafter, the gas 10 is discharged as the clean gas 15 into the refrigerator 7.
The conventional microbe propagation preventing apparatus is constructed as set forth above, that is, the conventional apparatus is not provided for purpose of the prevention of the microbe propagation by using the ion. Further, when the ozone is decomposed by the ozone decomposing catalyst 5, a generating negative ion contacts a case body of the ozone decomposing catalyst 5 to recombine with the case body since the ozone decomposing catalyst 5 includes the metallic case body. As a result, there are several problems in that, for example, the microbe propagation can not sufficiently be prevented due to the reduction of the generating negative ion.
On the other hand, in case microbe propagation is prevented by using the ozone, it is necessary to reduce the ozone concentration in the gas 10 to the range no more than 0.1 ppm in view of adverse effects to the human body. Accordingly, there are other problems in that, for example, the microbe propagation can not sufficiently be prevented in the reduced ozone concentration.